The factors in normal urine that inhibit stone formation, as compared to stone-formers urine and aqueous solution, will be identified. Ultrafiltration, dialysis, precipitation, ion exchange, and gel chromatography will be used to separate and identify inhibitor fractions, especially to determine the (presumably charged) groups responsible for inhibition. Studies of agglomeration and surface charge in calcium oxylate crystals growing in artificial urines containing additives and urine fractions will be carried out.